From 1bf3751ec90cc3174e01f0d701e8449ce163d113 Mon Sep 17 00:00:00 2001 From: Johannes Berg Date: Sun, 9 Dec 2012 23:41:06 +0000 Subject: [PATCH] ipv4: ip_check_defrag must not modify skb before unsharing ip_check_defrag() might be called from af_packet within the RX path where shared SKBs are used, so it must not modify the input SKB before it has unshared it for defragmentation. Use skb_copy_bits() to get the IP header and only pull in everything later. The same is true for the other caller in macvlan as it is called from dev->rx_handler which can also get a shared SKB. Reported-by: Eric Leblond Cc: stable@vger.kernel.org Signed-off-by: Johannes Berg Signed-off-by: David S. Miller --- net/ipv4/ip_fragment.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c index 448e68546827..8d5cc75dac88 100644 --- a/net/ipv4/ip_fragment.c +++ b/net/ipv4/ip_fragment.c @@ -707,28 +707,27 @@ EXPORT_SYMBOL(ip_defrag); struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user) { - const struct iphdr *iph; + struct iphdr iph; u32 len; if (skb->protocol != htons(ETH_P_IP)) return skb; - if (!pskb_may_pull(skb, sizeof(struct iphdr))) + if (!skb_copy_bits(skb, 0, &iph, sizeof(iph))) return skb; - iph = ip_hdr(skb); - if (iph->ihl < 5 || iph->version != 4) - return skb; - if (!pskb_may_pull(skb, iph->ihl*4)) - return skb; - iph = ip_hdr(skb); - len = ntohs(iph->tot_len); - if (skb->len < len || len < (iph->ihl * 4)) + if (iph.ihl < 5 || iph.version != 4) return skb; - if (ip_is_fragment(ip_hdr(skb))) { + len = ntohs(iph.tot_len); + if (skb->len < len || len < (iph.ihl * 4)) + return skb; + + if (ip_is_fragment(&iph)) { skb = skb_share_check(skb, GFP_ATOMIC); if (skb) { + if (!pskb_may_pull(skb, iph.ihl*4)) + return skb; if (pskb_trim_rcsum(skb, len)) return skb; memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));